This invention relates to a pliable member incorporating an electrically operated heating element, such as an electric blanket, mattress pad, heating pad or the like, and more particularly to an arrangement for positioning a heating element within the pliable member so as to prevent the adverse consequences that can result from exposure of the heating element to tensile forces or other conditions that can cause strain on the heating element.
A pliable electric heating member, such as an electric blanket, mattress pad, heating pad, throw or the like, typically includes a soft pliable outer member or shell formed of two layers between which one or more heating elements, such as resistive heating wires, are located. In a typical construction, the heating wires are generally parallel and spaced apart from each other, and are maintained in place via a stitching arrangement or a web-type material secured to one of the layers about each heating wire. Each heating wire is supplied with electrical power from a power supply, and the resistance of the heating wires functions to generate heat to provide a warm environment for the user of the electric blanket, heating pad or throw.
In a conventional construction, the heating wires are arranged in a linear orientation parallel to each other. While this type of heating wire configuration provides satisfactory operation, it involves certain disadvantages in that the heating wires have little or no xe2x80x9cgivexe2x80x9d. This can result in the heating wires becoming broken or disconnected from the power input of the pliable heating member, such as when a concentrated load (e.g. a user""s elbow or knee) is applied to a portion of the pliable member within which the heating wire is located, which results in application of tensile forces to the heating wires. Such breaking of the heating wires or disconnection of the heating wires from the power input can occur in any condition that causes stretching of the blanket material, and thereby the heating elements, beyond the capability of the heating wires to accommodate the tensile forces applied to the heating wires.
It is an object of the present invention to provide a heating element arrangement for a pliable heating member such as an electric blanket, mattress pad, heating pad, throw or the like which eliminates the adverse consequences associated with the heating element being subjected to tensile forces, which can result from application of concentrated loads to the pliable heating member. It is a further object of the invention to provide such a heating element arrangement which provides even distribution of heat throughout the area of the pliable heating member within which the heating element is contained. It is a further object of the invention to provide such a heating element arrangement which provides little or no additional cost of materials or in labor associated with manufacture of the pliable heating member. It is a further object of the invention to provide such a heating element arrangement which can be incorporated into the pliable heating member in various ways.
In accordance with the present invention, a heating device such as an electric blanket, mattress pad, heating pad or throw, includes a pliable member having first and second oppositely facing surfaces, and at least one elongated heating element located between the first and second oppositely facing surfaces. The pliable member defines a series of passages, and an elongated heating element is located within each passage. The elongated heating element in each passage has a non-linear configuration, such that the overall length of the elongated heating element contained within the passage exceeds the length of the passage. In this manner, application of a concentrated load to the pliable member, which normally results in the elongated heating elements experiencing a tensile force, enables the heating elements to flex and stretch within the passages to prevent the adverse effect on the heating elements caused by application of tensile forces to the heating elements, such as breakage or disconnection from the power input.
The pliable member preferably defines an interior within which the one or more passages are formed. The passages open onto open end areas that establish communication between adjacent passages. The heating elements in each pair of adjacent passages define a connector portion located in one of the open areas, such that the heating elements are preferably formed of a single length of heating wire that extends back and forth within the passages throughout the area of the pliable member. The heating wire defines a pair of ends, which are secured to a heating wire connector mounted to a circuit board, which in turn has a connector for receiving power from a power supply. In a preferred form, the heating wire in each passage has a wave-type or sinusoidal configuration throughout the extent of the passage.
The invention contemplates a heating device having a heating element arrangement as set forth above, as well as an improvement in a heating device having a pliable member and a method of positioning heating elements within an interior defined by a pliable member, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.